ガラス基板上に低温成長させた多結晶シリコン薄膜の構造に与えるハロゲンの影響

概要

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Polycrystalline silicon thin films were fabricated by VHF(100-144 MHz)plasma enhanced chemical vapor deposition. Three different source materials were used to grow the films on glass substrates : (1)SiH_2Cl_2/H_2, (2)SiF_4/H_2 and(3)SiH_4/H_2 mixing gases. It was found that the gas mixing ratio where crystal silicon grows strongly depends on the selection of source gas : i.e., crystal growth occurred at mixing ratios(SiF_4/H_2)smaller than 30/10 sccm while the crystal growth in SiH_4/H_2 system required much smaller mixing ratios, such as =1/50 sccm. Microstructures of the films were also strongly influenced by the source material. (220)orientation structures were easily obtained when SiF_4, SiH_2Cl_2 or B_2H_6 were used, compared to SiH_4. In addition, (400)preferentially oriented film grew on glass when the film was grown at a gas mixing ratio of SiF_4/H_2=30/10 sccm and a substrate temperature of 200°C. Chlorinated source gases including SiH_nCl_m(n+m=4)are also expected to produce(400)oriented growth.
1999-11-01